N–TiO2 nanoparticles embedded in silica prepared by Ti ion implantation and annealing in nitrogen

Room-temperature Ti ion implantation and subsequent thermal annealing in N2 ambience have been used to fabricate the anatase and rutile structured N-doped TiO2 particles embedded in the surface region of fused silica. The Stopping and Range of Ions in Matter (SRIM) code simulation indicates a Gaussian distribution of implanted Ti, peaked at ∼75 nm with a full width at half maximum of ∼80 nm. However, the transmission electron microscopy image shows a much shallower distribution to depth of ∼70 nm. Significant sputtering loss of silica substrates has occurred during implantation. Nanoparticles with size of 10–20 nm in diameter have formed after implantation. X-ray photoelectron spectroscopy indicates the coexistence of TiO2 and metallic Ti in the as-implanted samples. Metallic Ti is oxidized to anatase TiO2 after annealing at 600 °C, while rutile TiO2 forms by phase transformation after annealing at 900 °C. At the same time, N–Ti–O, Ti–O–N and/or Ti–N–O linkages have formed in the lattice of TiO2. A red shift of 0.34 eV in the absorption edge is obtained for N-doped anatase TiO2 after annealing at 600 °C for 6 h. The absorbance increases in the ultraviolet and visible waveband.